Urban sprawl has been discussed extensively with regard to its negative impacts. On this basis, regulations have been put in place to control sprawling suburbanization, including the establishment of restricted areas for expansion defined by administrative urban boundaries. Overall, these measures have not been at all successful, considering that city-regions continue to expand inorganically, often reinforcing urban sprawl patterns. As clear evidence of the weaknesses of planning regimes of control, these unsuccessful attempts are partly explained by a series of policy ambiguities that contradict the meaning of planning as a prescriptive discipline. This ambiguity is justified by the need to frame flexible regulations that allow adaptation to unforeseen events over time. In this paper, using the case of Auckland, New Zealand, it is demonstrated that instead of planning flexibility, there is planning “ambiguity” accompanied by weak opposition from rural regimes, which deliberately contributes to urban sprawl. This is relevant considering that the inorganic encroachment of rural lands diminishes the huge environmental potential of the peri-urban space of Auckland, its ecosystem services, and agricultural activities—all elements that encourage the creation of more environmentally sustainable peripheral landscapes as a counterpoint to traditional sprawling suburbanization.